WHEAT IS ONE OF THE MAJOR FIELD CROPS GROWN FOR FOOD AND CONTRIBUTES 20% TO GLOBAL CALORIE CONSUMPTION. US IS A MAJOR EXPORTER OF WHEAT. HOWEVER, THE PROFITABILITY OF GROWING WHEAT IN THE US HAS DIMINISHED IN RECENT YEARS, AND WHEAT PRODUCTION HAS BEEN REDUCED BY ABOUT 900 MILLION BUSHELS (24.5 MILLION TONS) (USDA-ERS, 2019). OUR LONG-TERM GOAL IS TO INCREASE THE YIELD OF WHEAT AND ENSURE PROFITABLE AND SUSTAINABLE WHEAT PRODUCTION IN THE US AND ALLEVIATE GLOBAL FOOD INSECURITY. THE FOCUS OF OUR PROJECT IS TO ENHANCE RESOURCE USE EFFICIENCY AND YIELD OF WHEAT THROUGH DEVELOPING CULTIVARS WITH OPTIMAL TILLER NUMBER. TILLERING /SHOOT BRANCHING IS A MAJOR YIELD COMPONENT AND A TARGET FOR ENHANCING THE YIELD OF WHEAT AND OTHER CEREAL CROPS. MODERN WHEAT CULTIVARS DEVELOP UP TO 15 TILLERS. SOME OF THE TILLERS ARE NOT PRODUCTIVE BECAUSE THEY SENESCE BEFORE GIVING YIELD. THEREFORE, MOST OF THE GRAIN YIELD IS CONTRIBUTED BY THE MAIN SHOOT AND A FEW PRODUCTIVE TILLERS THAT REACH MATURITY AND PRODUCE GRAINS. THE UNPRODUCTIVE TILLERS COMPETE FOR WATER, NUTRIENTS, AND LIGHT WITH THE PRODUCTIVE SHOOTS. THE COMPETITION FOR RESOURCES REDUCES THE YIELD OF THE PRODUCTIVE SHOOTS. WE HYPOTHESIZE THAT A WHEAT PLANT WITH TWO TO THREE PRODUCTIVE TILLERS AND RESTRICTED GROWTH OF UNPRODUCTIVE TILLERS WILL BE THE IDEAL PLANT ARCHITECTURE FOR OPTIMAL YIELD. THE TILLER INHIBITION (TIN) MUTANT WHEAT IS IDEAL FOR TESTING THIS HYPOTHESIS AND IDENTIFYING THE PHYSIOLOGICAL AND MOLECULAR MECHANISMS NEEDED TO DEVELOP WHEAT CULTIVARS WITH THE IDEAL PLANT ARCHITECTURE.TILLER INHIBITION IN TIN IS DUE TO PRECOCIOUS INTERNODE DEVELOPMENT THAT INDIRECTLY AFFECTS THE GROWTH OF TILLERS. IN WHEAT, TILLERS GROW DURING THE VEGETATIVE STAGE, AND STEM INTERNODES BEGIN TO ELONGATE DURING THE FLOWERING STAGE. A GROWING STEM, WHICH IS A STRONG SINK FOR SUGARS, INHIBITS TILLER GROWTH INDIRECTLY BY LIMITING THE SUPPLY OF SUGARS FROM THE MAIN SHOOT TO TILLER BUDS. ALTHOUGH BOTH TIN AND THE NEAR-ISOGENIC WILD-TYPE (WT) TRANSITION TO FLOWERING SIMULTANEOUSLY, THE STEM INTERNODES IN TIN START TO ELONGATE EARLIER THAN THE STEM INTERNODES IN THE WT. THE EARLY INTERNODE ELONGATION SHORTENS THE TILLERING PHASE OF TIN. THEREFORE, TIN PLANTS PRODUCE UP TO TWO TILLERS, WHEREAS THE WT PLANTS WITH A LONGER TILLERING PHASE PRODUCE UP TO 10 PRIMARY AND HIGHER-ORDER TILLERS. THE SPIKE LENGTH AND GRAIN NUMBER OF THE MAIN SHOOT OF TIN IS TWICE THAT OF WT. THEREFORE, REDUCTION IN TILLERING IN TIN IS ASSOCIATED WITH HIGHER YIELDS. HOWEVER, THE TENDENCY OF TIN PLANTS TO STUNTING IN LONG DAYS AND LOW TEMPERATURES (THERMO-PHOTOPERIODIC SENSITIVITY) HAS BEEN A BARRIER FOR USING TIN IN BREEDING WHEAT CULTIVARS WITH REDUCED TILLER NUMBER. ALSO, STUNTING IN TIN IS ASSOCIATED WITH ABNORMAL INTERNODE GROWTH. THEREFORE, THIS PROJECT HAS THE FOLLOWING TWO OBJECTIVES: A) MODULATING INTERNODE ELONGATION IN TIN INDIRECTLY BY INDUCING FLOWERING AT DIFFERENT TIMES AND INVESTIGATING ITS EFFECT ON TILLER NUMBER AND YIELD; AND B) TRANSCRIPTOME ANALYSIS TO IDENTIFY MOLECULAR MECHANISMS CONTROLLING PRECOCIOUS INTERNODE ELONGATION AND STUNTING IN TIN. THROUGH THIS PROJECT, WE WILL GENERATE DATA ON OPTIMAL TILLER NUMBER THAT SHOULD MAXIMIZE WHEAT YIELD BY MODULATING TILLERING IN TIN INDIRECTLY THROUGH CHANGING FLOWERING TIME (TIMING OF INTERNODE ELONGATION). WE WILL ALSO GENERATE TRANSCRIPTOME DATA THAT SHOULD PROVIDE NEW INSIGHTS INTO THE MOLECULAR BASIS OF PRECOCIOUS INTERNODE ELONGATION AND STUNTING IN TIN.